A number of types of continuous tube type drippers are known. One type comprises a cylindrical body having a pressure reducing pathway formed on the outer surface thereof, which pathway engages the inner surface of a continuous tube extruded thereabout. It has also been proposed to insert an intermediate layer of material interposed between the pressure reducing pathway of the cylindrical body and the continuous tube.
Another type of continuous tube dripper employs self-contained flow controlled dripper elements which are attached to the inner wall of a continuous tube and provided with outlet apertures therethrough.
All of the above-described drip irrigation apparatus suffers from a number of disadvantages. Significant among these is the requirement for extremely accurate outlet aperture formation in the continuous tube such that the outlet aperture corresponds to the outlet from the pressure reducing pathway. Both linear and radial positioning of the aperture must be achieved with significant accuracy. This requires relatively sophisticated and expensive machinery.
Another difficulty encountered in the manufacture of the conventional continuous tube dripper apparatus arises in the feeding of the interior elements to the extruder which forms the outer tube. Where the interior elements are cylindrical, they cannot be fed on a track located interiorly thereof and thus difficulties of alignment are encountered. Where discrete elements are employed, which do not fill the radius of the cross section of the outer tube, complex apparatus and techniques for positioning the discrete elements on the tube are required.